1. Field of the Invention
The field of this invention relates to bicycles and more particularly to a novel crank arm for a bicycle that interconnects between the pedal and the hub bearing assembly of the bicycle.
2. Description of the Prior Art
Within recent years, bicycles have made a significant come-back and are being extensively used by a large number of people. Bicycles are not only used for pleasure riding but are used extensively in competition. It makes sense that the lighter the bicycle, the more the advantage the user has in a competitive situation. In the past, in order to make bicycles lighter, bicycles have been constructed out of newer, stronger, lighter materials such as titanium and magnesium. These materials are utilized not only in constructing of the wheels of the bicycle, but also in construction of the frame.
Every part of the bicycle is now being designed with weight reduction in mind and also to maximize strength. A common part for a bicycle is a crank arm with there being two crank arms located one hundred eighty degrees apart relative to the hub bearing assembly. Connected to the outer end of each crank arm is a pedal and these pedals are to be utilized by the user's legs to apply the force resulting in movement of the bicycle.
In the past, there has been some effort at designing these crank arms to be constructed of stronger, lighter material. These crank arms directly transfer the muscle power of the user into the propelling force of the bicycle. Therefore, these crank arms are subjected to a significant amount of torque. It is common for a bicycle to be operated by the user over an extended period of time (such as several hours) and the bicycle be ridden up and down hills for many miles. Also, it is common for users to be quite strong individuals capable of applying a substantial amount of torque through the crank arms. The continuous application over an extended period of time of such a high degree of torque over several weeks or months has resulted in breaking of these crank arms.
It has been found that the most common point of breakage is at the outer end of the crank arm where the pedal is connected to the crank arm. In the constructing of these lightweight crank arms, the outer end of the crank arm includes a plug. This plug includes a threaded opening which facilitates attachment to the pedal. In the past, it has been common to construct a plug to be cylindrical in exterior configuration. The only securement between the plug and the remaining portion of the crank arm is by conventional welding. If this welding breaks down, the plug will merely rotate relative to the crank arm since the exterior configuration of the plug is circular.
There is a need to construct the crank arm of a bicycle to be stronger to lessen the possibility of failure even when an excessive force is being continuously applied by a user over an extending period of time without increasing the weight of the crank arm. A few ounces of decreased weight can go a long way toward giving a particular rider a significant competitive advantage in a bicycle race.